Telephone transmitter



(No Model.) 2 Sheets-Sheet 1.

J. F. BAHR.

TELEPHONE TRANSMITTER.

No. 377,475. Patented Feb. 7, 1888.

WITNESSES:

EH5. Phololilhogmphir. WINMIMI. D l

UNTTED f STAT S- PATENT Ori ice. f

JOHN, F. 'BAHR, or JERSEY CITY, NEW JERSEY.

TELEPHONE-TRANSMITTER.

srEcIricA'rrorv forming part of Letters Patent No'.'377,4'75, dated February '1, 1888.

Application filed March 28, 1887.

To all whom it may concern/.- I

Be it known that 1, JOHN F. BAHR,a citizen of the United States, residing at JerseyGity,

in the county of Hudson and, State of New tion, such as will' enable others. skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to the letters of reference marked thereon, which form a part of this specification.

g The object of this invention is to more per} fectly transmit articulate speech through an electrical conductor to a distant station, to provide a durable, convenient, and reliable telephone-transmitter, and to reduce the cost of manufacture.

A further object is to provide atransmitter for table or desk use of increased convenience as well as efficiency.

Theinvention consists inan improved telephone-transmitter, and in the arrangements and combinations of parts, substantially as will be hereinafter set forth, and finally embodied in the clauses of the claim.

Referring to the accompanying drawings, in which like letters represent corresponding parts in each of the several figures of the two sheets thereof, Figure 1, Sheet 1, represents a top view ofa transmitter embodying my improvement. Fig. 2 is a top View of the same with the cover removed, showing a set of carbon plates in plan. Fig. 3 is a section through line av, Fig. 2. Fig. 4 is a detail, in side elevation, of the upper-carbon plate, and Fig. 5 a plan of the lower plate. Fig.' 6 is a side elevation of the transmitter-plates in circuit with an induction-coil and battery, portions of the sounding-board and case being broken away. Fig. 7, Sheet 2, is. a side elevation of a modification, showing a certain horn or funnel-shaped tube for conducting the sound, so as to strike the plates at the proper place; and Fig. 8 is a vertical transverse sectional view showing a way of arranging a sounding-board so as to accomplish the same result.

In said drawings is shown a box, case, or frame constructed preferably, as indicated in thereof.

Figs. 1, 2, and 3, with side and bottom boards,

Serial No. 232,638. (No model.)

parts which are particularly effective in transmitting the sound, the said cover readily al-- lowing access to said transmitting mechanism "by opening the same, andprotecting said mechanism from dust and from injury by con tact with articles such as are ordinarily found upon a desk of an office. The said cover 12 is centrally perforated, the perforation c contracting toward the interior of the box to con-. centrate thesound-waves upon the-plate e. j

' The said cover b also operates to hold the said plate 6 (which simply rests upon an. under .plate bygravity) within the box, preventing its f'al1ing,when thedevice is being transported,

from proper relation to its cooperating parts.

Within the box or case is arranged a partition, d, of resonant material. This is securely held in place upon suitable bearings at the edges thereof, as indicated in Fig. 3, the central portions of the board being away from any support, so that considerable elasticity or vibratory action is secured at the center serves as a sounding-board, which coactswith the-plates above referred to to transmit.v the The said partition in one sensethus sound articulations with greater perfection.

The said sounding board or partition d separates the space within the boxinto two chambers, of which the upper one may be opened to receive the plates 0 and f, and is closed or partly closed by the hinged and perforated:

cover. The under or lower chamber serves as areception-chamber for the induction-coil R, the same being held therein, where it will lie concealedand protected from damage.

The plates 6 and f are preferably of' thin disks of carbon or other conductor of electricity, carbon being preferred because it may readily be molded or pressed into the desired shape,- its peculiar susceptibility lto sound;

' waves, and other qualities which render it peculiarly adapted for the purpose.

Uponthe partition d is first secured the under plate, d, preferably by gluing, so that the said platehas'a rigid connection and may vibrate therewith under the influence of the sound-waves. Said under'plate is provided with receptaclesk. is k, adapted to receive corresponding projectionsron the under side of the upper plate and prevent the saidupper plate from being thrown laterally from proper 1 relation to the under plate by such slight jars as are liable to occur on a table, and yet the said plates, or at least the upper movable plate, is given freedom to move vertically or to increase and diminish its pressure on the lower plate'under the influenceof the soundwaves. The said plates are furthermore held in their approximate positions by the coiled and spring-like conducting-wires g and the cover of the box.

As before intimated, the plate 0 is provided on its lower side with projections or points 6, preferably three in number. These are adapted to rest in corresponding depressions, k, in the lower plate, f, both plates remaining in an approximately horizontal position, the upper plate simply lying on the lower plate by the force of gravity, and thus very sensitive to the sound-waves. The upper plate is larger than the opening in the cover, so that it cannot pass through said opening through accident in transportation, and the edges of said plate will thus lie concealed and the appearance of the transmitter will be improved.

Both the upper and lower'plates are connected, by means of an electrical conductor, as g, with a battery, h, and the primary winding wires of aninduction-coil, R. Th us the current is obliged to pass through the points i, resting in the depressions k of the lower plate, so that when sound-waves strike the plate the resistance of the circuit is changed by the greater or less pressure upon said plates, as will be -understood. Therefore the current passing m in circuit with the secondary winding-wires of the induction-coil, and thence along to the receiver at a distant station, and there reproducing articulate speech in the ordinary manner. The lower plate, f, is preferably secured to a sounding-board, as d, thus giving said plate a vibratory motion when disturbed by the voice, this reproducing a clearer, sharper sound on the receiver by means of theprimary current being more sharply defined in its variations, and thus affecting the secondary current in a similar manner, as will be manifest. The said plates require no adjustment after having been once set in place, as gravity is always constant, and that force is'the only one that acts upon the plates when in their normal condition; WVhen disturbed by the voice, the air-waves act alternately with and against the force of gravity to lessen or increase the resistance offered to the electric current passing through the contact-points t, and thus causing like variations in the secondary or transmitted current.

When it is preferable to speak through an opening in a vertical plane instead of in a horizontal, a funnel-shaped tube, as n, may be attached to the mouth-piece or opening of the transmitter, as illustrated in Fig. 7. Said funnelshaped tube is curved, so as to direct the sound vertically upon the carbon plates. In lieu of the horn or funnel-shaped tube, a sounding-board, as 0, Fig. 8, may be used, when set at the requisite angle, and will answer the same purpose.

The plates 6 and f are preferably made of carbon; but I do not wish to limit myself, as there are metals which will answer the same purpose in some cases with equally as good effect; neither do I-wish to limit myself to the exact form and proportion of parts, as it is evident that changes may be made inthose particulars without in any way departing from the spirit or scope of iny invention.

I am aware of the devices and features of invention shown and described in United States Patents Nos. 231,226, 250,307, 266, 043, 307 ,026. 339,499, 351,569, and English Patents No. 4,296 of 1884 and No. 1,156 of 1885, and I do not wish to be understood as claiming the same herein.

Having thus fully described my invention, what I claim as new is- 1. Theimproved telephonetransmitterherein described, combining therein a box or case having a perforated cover or lid. a partition separating the interior of said box into two chambers, plates fe, one of which is secured to said partition and the other of which lies, under the influence of gravity, upon the first one, and is provided with projections 7', and suitable conducting-wires, allsaid parts being arranged and adapted to operate substantially as set forth.

2. Theimproved telephone-transmitter,combining a box or case with a perforated cover, a sounding-board secured therein, a carbon plate secured upon said sounding-board, a carbon plate provided with projections and lying by gravity upon the first said plate, and conducting-wires g 9, said parts being arranged and combined substantially as and for the purposes set forth.

3. The improved transmitter, substantially as described, combining therein a box or case, a hinged and perforated cover, a partition secured in said box at its edges and forming upper and lower' chambers, a carbon plate, f, secured upon said partition and having depressions k it, an upper carbon plate, 6, having contact-points Mi, corresponding with said depressions, said plate e lying on said plate f by gravity, and conducting-wires g g, and an induction-coil arranged in said lower chamber, all said parts being arranged and adapted to operate substantially as and for the purposes set forth.

In testimony that I claim the foregoing I have hereunto set my hand this 26th day of March, 1887.

JOHN F. BAI-IR.

\Vitnesses:

THOMAS MoFFERr, HENRY REUHL. 

